A slang term to describe Microsoft's true/false/error scheme used in many places in the Win32 API. It's used to describe when
something has 3 states, as compared to Boolean, which has two states (
usually true or false).
The GetMessage API is an
interesting example of the bizarre Microsoft Troolean (as opposed to
traditional, Boolean) logic. GetMessage is defined to return a BOOL, but the
documentation specifies three types of returns, non-zero, zero and -1. I am not making it up! Here's an excerpt from the help file:
* If the function retrieves a message other than WM_QUIT, the return value is nonzero.
* If the function retrieves the WM_QUIT message, the return value is zero.
* If there is an error, the return value is -1.
Excerpt from Reliable Software, LLC